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Versions: 00 01 02 03 draft-ietf-6renum-gap-analysis

Network Working Group                                           B. Liu
Internet Draft                                                S. Jiang
Intended status: Informational            Huawei Technologies Co., Ltd
Expires: June 7, 2012                                     B. Carpenter
                                                University of Auckland
                                                      December 5, 2011

                    IPv6 Site Renumbering Gap Analysis
                   draft-liu-6renum-gap-analysis-03.txt


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 7, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Abstract

   This document briefly introduces the existing mechanisms could be
   utilized by IPv6 site renumbering and envisions the effort could be
   done. This document tries to cover the most explicit issues and



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   requirements of IPv6 renumbering. Through the gap analysis, the
   document provides a basis for future work to identify and develop
   solutions or to stimulate such development as appropriate. The gap
   analysis is presented following a renumbering event procedure clue.



Table of Contents


   1. Introduction ................................................. 3
   2. Overall Requirements for Renumbering ......................... 3
   3. Existing Components for IPv6 Renumbering ..................... 4
      3.1. Relevant Protocols and Mechanisms ....................... 4
      3.2. Management Tools ........................................ 5
      3.3. Procedures/Policies ..................................... 5
   4. Managing Prefixes ............................................ 6
      4.1. Prefix Delegation ....................................... 6
      4.2. Prefix Assignment ....................................... 6
   5. Address Configuration ........................................ 6
      5.1. Host Address Configuration .............................. 6
      5.2. Router Address Configuration ............................ 8
      5.3. Static Address Configuration ............................ 9
   6. Updating Relevant Address Entries ............................ 9
      6.1. DNS Records Update ...................................... 9
      6.2. In-host Server Address Update .......................... 10
      6.3. Filters ................................................ 10
   7. Renumbering Event Management ................................ 11
      7.1. Renumbering Notification ............................... 11
      7.2. Synchronization Management ............................. 11
      7.3. Renumbering Monitoring ................................. 11
   8. Miscellaneous ............................................... 12
      8.1. Mobility ............................................... 12
   9. Gaps considered unsolvable .................................. 12
      9.1. Address Configuration .................................. 12
      9.2. Address Relevant Entries Update ........................ 12
      9.3. Miscellaneous .......................................... 13
   10. Security Considerations .................................... 13
   11. IANA Considerations......................................... 13
   12. References ................................................. 13
      12.1. Normative References .................................. 13
      12.2. Informative References ................................ 14
   13. Acknowledgments ............................................ 15






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1. Introduction

   As introduced in [RFC5887], renumbering, especially for medium to
   large sites and networks, is currently viewed as an expensive,
   painful, and error-prone process, avoided by network managers as much
   as possible. If IPv6 site renumbering continues to be considered
   difficult, network managers will turn to Provider Independent (PI)
   addressing for IPv6 to attempt to minimize the need for future
   renumbering. However, widespread use of PI may create very serious
   BGP4 scaling problems. It is thus desirable to develop tools and
   practices that may make renumbering a simpler process to reduce
   demand for IPv6 PI space.

   This document performs a gap analysis to provide a basis for future
   work to identify and develop solutions or to stimulate such
   development as appropriate. The gap analysis is organized by the main
   steps of renumbering process, which include prefix management, node
   address (re)configuration, and updating relevant address entries in
   various gateways, routers and servers, etc. Besides these steps, the
   aspect of renumbering event management is presented independently,
   which intends to help the operational/administrative process. It is
   expected that these steps and management could cover all the aspects
   of an renumbering event.

   This document draws on existing work in (at least) [RFC5887], [I-
   D.chown-v6ops-renumber-thinkabout] and [RFC4192]. Contributions from
   [I-D.jiang-6renum-enterprise] are incorporated into the more detailed
   analysis. Lots of issues were analyzed in RFC5887 & [I-D.chown-v6ops-
   renumber-thinkabout], but many of them are out of 6renum scope or
   unsolvable.  This document intends to identify the valuable and
   solvable issues, dig out of some undiscovered gaps, and tries to give
   solution suggestions.

2. Overall Requirements for Renumbering

   This section introduces the overall ultimate goals we want to achieve
   in a renumbering event. In general, we need to leverage renumbering
   automation to avoid human intervention as much as possible at
   reasonable cost. Some existing mechanisms have already provided
   useful help. Further efforts may be achieved in the future.

   The automation can be divided into four aspects as follows, which are
   also the gap analysis topics.




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   o Prefix delegation and delivery should be automatic and accurate in
      aggregation and coordination.

   o Address reconfiguration should be automatically achieved through
      standard protocols with minimum human intervention.

   o Updating relevant address entries should be performed integrally
      and without error. [Open Question]Is it necessary to develop
      automatic entries update mechanisms? If necessary, do we need
      standard protocols/interface for it?

   o Renumbering event management is needed to provide the functions of
      renumbering notification, synchronization, and monitoring .etc.

   Besides automation, session survivability is another important issue
   during renumbering since application outage is one of the most
   obvious impacts that make renumbering painful and expensive. We have
   an enormous advantage in IPv6 which is the ability to overlap the old
   and new prefixes and to use the address lifetime mechanisms in SLAAC
   and DHCPv6. That is fully described in [RFC4192]. We consider this
   mechanism is sufficient for session survivability issue in most of
   the cases.

   [Open Question]Should we consider the case of very long-lived
   application sessions (days or weeks) which cannot be resolved by
   [RFC4192]?

3. Existing Components for IPv6 Renumbering

   Since renumbering is not a whole new issue, some protocols/mechanisms
   have been already utilized or even be developed dedicated for
   renumbering. However, generally current renumbering is achieved by
   existing protocols rather than dedicated renumbering protocols. This
   section briefly reviews these existing protocols/mechanisms to
   provide a basis for the gap analysis.

3.1. Relevant Protocols and Mechanisms

   o RA messages, defined in [RFC4861], are used to deprecate/announce
      old/new prefixes and to advertise the availability of an upstream
      router. In renumbering, it is one of basic mechanisms for host
      configuration.

   o When a host is renumbered, it may use SLAAC [RFC4862] for address
      configuration with the new prefix. Hosts receive RA messages which
      contain routable prefix(es) and the address(es) of the default
      router(s), then hosts can generate IPv6 address(es) by themselves.


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   o Hosts configured through DHCPv6 [RFC3315] can reconfigure
      addresses by initialing RENEW sessions when the current addresses'
      lease time are expired or they receive the reconfiguration
      messages initiated by the DHCPv6 servers.

   o DHCPv6-PD (Prefix Delegation) [RFC3633] enables automated
      delegation of IPv6 prefixes using the DHCPv6.

   o [RFC2894] defined standard ICMPv6 messages for router renumbering.
      This is a dedicated protocol for renumbering, but has not been
      widely used.

3.2. Management Tools

   Some operations of renumbering could be automatically processed by
   management tools in order to make the renumbering process more
   efficient and accurate. The tools may be designed dedicated for
   renumbering or just common tools could be utilized for some
   operations in renumbering.

   Following are samples of the tools.

   o Address management tools. There are both commercial and open-
      source, and even home-made solutions.
      [Further work is needed to identify what an address management
      tool should be able to do for improving the ability of managing a
      network through a renumbering event.]

   o [LEROY] proposed a mechanism of macros to automatically update the
      address relevant entries/configurations inside the DNS, firewall,
      etc. The macros can be delivered though SOAP protocol from a
      network management server to the managed devices.

   o Asset management tools/systems. These tools may provide the
      ability of managing configuration files in nodes so that it is
      convenient to update the address relevant configuration in these
      nodes.

3.3. Procedures/Policies

   o [RFC4192] proposed a procedure for renumbering an IPv6 network
      without a flag day. The document includes a set of operational
      suggestions which can be followed step by step by network
      administrators.





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   o [I-D.jiang-6renum-enterprise] analyzes the enterprise renumbering
      events and gives the recommendations among the existing
      renumbering mechanisms. According to the different stages,
      renumbering considerations are described in three categories:
      considerations and recommendations during network design, for
      preparation of enterprise network renumbering, and during
      renumbering operation

4. Managing Prefixes

   When renumbering an enterprise site, a short prefix may be divided
   into longer prefixes for subnets. So we need to carefully manage the
   prefixes for prefix delivery, delegation, aggregation,
   synchronization, coordination, etc.

4.1. Prefix Delegation

   Usually, the short prefix comes down from the operator and received
   by DHCPv6 server or router inside the enterprise network. The short
   prefix could be automatically delegated through DHCPv6-PD. Then the
   downlink DHCP servers or routers can begin advertising the longer
   prefixes to the subnets.

   For the delegation routers, they may need to renumber themselves with
   the delegated prefixes. We need to consider the router renumbering
   issue which cannot be covered by DHCP-PD only.

4.2. Prefix Assignment

   When subnet routers receive the longer prefixes, they can directly
   assign them to the hosts. The prefix assignment overlaps with the
   host address configuration, which is described in the following
   section 5.1.

5. Address Configuration

5.1. Host Address Configuration

   Both of the DHCPv6 and ND protocols have IP address configuration
   function. They are suitable for different scenarios respectively.
   During renumbering, the SLAAC-configured hosts can reconfigure IP
   addresses by receiving ND Router Advertisement (RA) messages
   containing new prefix information (It should be noted that, the
   prefix delivery could be achieved through DHCP according to the new
   IETF DHC WG document [I.D ietf-dhc-host-gen-id]). The DHCPv6-
   configured hosts can reconfigure addresses by initiating RENEW
   sessions when the current addresses' lease time are expired or


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   receiving the reconfiguration messages initiated by the DHCPv6
   servers.

   o SLAAC and DHCPv6 address configuration co-existence

        While an IPv6 site is being renumbered, both DHCPv6 and ND may
        be used to reconfigure the host addresses. The co-existence
        issue mainly includes following aspects:

        - Dynamic upstream learning

          [RFC5887] mentioned that, DHCP-configured hosts may want to
          learn about the upstream availability of new prefixes or loss
          of prior prefixes dynamically by deducing from periodic RA
          messages. But there is no standard specifying what approach
          should be taken by a DHCPv6-configured host when it receives
          RA messages containing new prefix. It depends on the operation
          system of the host and cannot be predicted or controlled by
          the network.

        - DHCP-managed hosts receiving RA messages

          It is unclear that whether a DHCP-managed host would accept
          configuration though RA messages, it depends on the policies
          in the host's operating system. If it ignores the RA messages
          and there are no DHCPv6 reconfiguration messages received
          either, the renumbering would fail.

        -  SLAAC-configured hosts finding DHCPv6 in use

          [RFC5887] mentioned RA message of ND protocol contains a
          "Managed Configuration" flag to indicate DHCPv6 is in use. But
          it is unspecified what behavior should be taken when the host
          receives RA messages with "M" set to 1. The gap of standard
          will cause ambiguous host behavior because it depends on the
          operation system of the host.

          The host may start a DHCPv6 session and receives the DHCPv6
          address configuration. It is also possible that the host finds
          the DHCPv6 assigned prefix is different from the prefix in the
          RA messages, which means multiple uplinks are available or
          there is a serious network configuration error.

          Another possibility is that the host may receive no response
          from any DHCPv6 servers, which means the DHCPv6 service is not
          available and the "Managed Configuration" flag was mis-
          configured.


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   o DHCPv6 reconfigure bulk usage

        [RFC5887] mentioned that "DHCPv6 reconfiguration doesn't appear
        to be widely used for bulk renumbering purposes".

        The reconfiguration defined in [RFC3315] needs to establish a
        session between DHCP server and client. This could be considered
        as a stateful approach which needs much resource on the server
        to maintain the renumbering sessions. This is probably one of
        the reasons that DHCP reconfiguration is not suitable for bulk
        usage.

        Another limitation of reconfiguration is that it only allows th
        e messages to be delivered to unicast addresses. So if we want
        to use it for bulk renumbering, stateless DHCPv6 reconfiguration
        with multicast may be needed. However, this may involve protocol
        modification.


5.2. Router Address Configuration

   o Learning new prefixes

        As described in [RFC5887], "if a site wanted to be multihomed
        using multiple provider-aggregated (PA) routing prefixes with
        one prefix per upstream provider, then the interior routers
        would need a mechanism to learn which upstream providers and
        prefixes were currently reachable (and valid).  In this case,
        their Router Advertisement messages could be updated dynamically
        to only advertise currently valid routing prefixes to hosts.
        This would be significantly more complicated if the various
        provider prefixes were of different lengths or if the site had
        non-uniform subnet prefix lengths."

   o Restart after renumbering

        "Some routers cache IP addresses in some situations. So routers
        might need to be restarted as a result of site renumbering"
        [RFC2072].


   o Router naming

        In [RFC4192], it is suggested that "To better support
        renumbering, switches and routers should use domain names for
        configuration wherever appropriate, and they should resolve
        those names using the DNS when the lifetime on the name


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        expires."
        As [RFC5887] described, this capability is not new, and at least
        it is present in most IPsec VPN implementations. But many
        administrators do not realize that it could be utilized to avoid
        manual modification during renumbering.

        In enterprise scenario, the requirement of router naming is not
        as strong as that in ISP. So for the administrators, the
        motivation of using router naming for easing renumbering may be
        not strong.

5.3. Static Address Configuration

   There is another draft dedicated to the static address issue. Please
   refer to [I-D.carpenter-6renum-static-problem].

6. Updating Relevant Address Entries

   When nodes in a site have been renumbered, then all the entries in
   the site which contain the nodes' addresses must be updated. The
   entries mainly include DNS records and filters in various entities
   such as ACLs in firewalls/gateways.

6.1. DNS Records Update

   o Dynamic DNS update

        For DNS records update, most sites will achieve it by
        maintaining a DNS zone file and loading this file into the
        site's DNS server(s).  Synchronization between host renumbering
        and the updating of its A6 or AAAA record is hard. [RFC5887]
        mentioned that an alternative is to use Secure Dynamic DNS
        Update [RFC3007], in which a host informs its own DNS server
        when it receives a new address.

        Secure Dynamic DNS Update has been widely supported by the major
        DNS systems, but it hasn't been widely deployed, especially in
        the host. Current practices mainly involve the DHCP servers
        which act as clients to request the DNS server to update
        relevant records. Normal hosts are not suitable to do this
        mainly because of the complexity of key management issues
        inherited from secure DNS mechanisms.







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6.2. In-host Server Address Update

   While DNS records addresses of hosts in servers, hosts also record
   addresses of servers such as DNS server, radius server, etc. While
   renumbering, the hosts must update the records if the server
   addresses changed. Addresses of DHCPv6 servers do not need to be
   updated. They are dynamically discovered using DHCPv6 relevant
   multicast addresses.

   o The DNS server addresses for hosts are configured by DHCPv6. But
      current DHCPv6 messages do not indicate to hosts the lifetimes of
      DNS. If the DNS lifetime expired and has been renumbered, the
      hosts may still use the old addresses. DHCPv6 should be extended
      to indicate to hosts the associated DNS lifetimes when making DNS
      configuration. How the DHCP server could know about the DNS
      lifetime is another issue.

6.3. Filters

   o Filters Management

        Filters based on addresses or prefixes are usually spread in
        various devices. As [RFC5887] described, some address
        configuration data might be widely dispersed and much harder to
        find, even will inevitably be found only after the renumbering
        event. So there's a big gap for filter management.

        In [LEROY], a server is used for managing filter update in
        various devices. But identifying where and which of the filters
        need to be updated during renumbering is still a gap.

   o Filter Update Automation Operation

        As mentioned in section 3.2, [LEROY] proposed a mechanism which
        can automatically update the filters. The mechanism utilizes
        macros suitable for various devices such as routers, firewalls
        etc. to update the filter entries based on the new prefix. Such
        automation tool is valuable for renumbering because it can
        reduce manual operation which is error-prone and inefficiency.

        Besides the macros, [LEROY] also proposed to use SOAP to deliver
        the macros to the devices. As well as SOAP we may consider
        whether it is possible and suitable to use other standardized
        protocols such as NETCONF.

        Update of filters based on prefixes and filters based on
        addresses may have different requirements and methods. Address-


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        based filters may be mainly with regard to domain names while
        prefix-based filters be relevant to more abstract entity (mask
        e.g.). Thus, we may consider different ways to update the two
        kinds of filters, for example, the prefix-based filters may
        consider to be updated though DHCPv6 server, which may provide
        better efficient.

7. Renumbering Event Management

   From the perspective of network management, renumbering is a kind of
   event which may need additional process to make the process more easy
   and manageable.

7.1. Renumbering Notification

   If hosts or servers are aware of a renumbering event happening, it
   may help the relevant process. Following are several examples of such
   additional process may ease the renumbering. Further contributions
   are expected.

   o A notification mechanism may be needed to indicate the hosts that
      a renumbering event of local recursive DNS happen or is going to
      take place.

   o [RFC4192] suggests that "reducing the delay in the transition to
      new IPv6 addresses applies when the DNS service can be given prior
      notice about a renumbering event." Reducing delay could improve
      the efficiency of renumbering.

7.2. Synchronization Management

   o DNS update synchronization

        DNS update synchronization focuses on the coordinating between
        DNS and other entities/mechanisms, for example, as described in
        [RFC5887], synchronizing the SLAAC and DNS updates, and of
        reducing the SLAAC lease time and DNS TTL.

7.3. Renumbering Monitoring

   While treating renumbering a network event, mechanisms to monitor the
   renumbering process may be needed. Considering the address
   configuration operation may be stateless (if ND is used for
   renumbering), it is difficult for monitoring. But for the DNS and
   filter update, it is quite possible to monitor the whole process.




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8. Miscellaneous

8.1. Mobility

   As [RFC5887] suggested, for Mobile IP, we need a better mechanism to
   handle change of home agent address while mobile is disconnected.

9. Gaps considered unsolvable

   This section lists gaps have been documented but are considered
   unsolvable or out of the scope of 6renum working group.

9.1. Address Configuration

   o RA prefix lifetime limitation

        In section 5.5.3 of [RFC4862], it is defined that "If the
        received Valid Lifetime is greater than 2 hours or greater than
        RemainingLifetime, set the valid lifetime of the corresponding
        address to the advertised Valid Lifetime." So when renumbering,
        if the previous RemainingLifetime is longer than two hours, it
        is impossible to reduce a prefix's lifetime less than two hours.
        This limitation is to prevent denial-of-service attack.


9.2. Address Relevant Entries Update

   o DNS entries commonly have matching Reverse DNS entries which will
      also need to be updated during renumbering.

   o DNS data structure optimization

        [RFC2874] proposed a new A6 record type for DNS recording IPv6
        address/prefix. And several extensions on query and processing
        were also proposed. With the A6 record and the extensions, an
        IPv6 address can be defined by using multiple DNS records. This
        feature increases the complexity of resolver but reduce the cost
        of zone file maintenance. So renumbering could be easier than
        AAAA record. But the [RFC2874] has not been widely used.

   o DNS authority

        As described in [I-D.chown-v6ops-renumber-thinkabout], "it is
        often the case in enterprises that host web servers and
        application servers on behalf of collaborators and customers
        that DNS zones out of the administrative control of the host
        maintain resource records concerning addresses for nodes out of


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        their control. When the service host renumbers, they do not have
        sufficient authority to change the records."

        It is an operational issue and this document considers it not
        suitable to be solved through bring additional
        protocol/mechanism to standardize the interaction between DNS
        systems needs to be considered.

9.3. Miscellaneous

   o For transport layer, [5887] said that TCP connections and UDP
      flows are rigidly bound to a given pair of IP addresses.

   o For application layer, as [5887] said, in general, we can assert
      that any implementation is at risk from renumbering if it does not
      check that an address is valid each time it opens a new
      communications session.

10. Security Considerations

   o Prefix Validation

   Prefixes from the ISP may need authentication to prevent prefix
   fraud. Announcing changes of site prefix to other sites (for example,
   those that configure routers or VPNs to point to the site in
   question) also need validation.

   In the LAN, Secure DHCPv6 ([I-D.ietf-dhc-secure-dhcpv6]) or SeND
   ([RFC3971], Secure Neighbor Discovery) deployment may need to
   validate prefixes.

   o Influence to Security Controls

   During renumbering, security controls (e.g. ACLs) blocking access to
   legitimate resources should not be interrupted.

11. IANA Considerations

   None.

12. References

12.1. Normative References

   [RFC2894] M. Crawford, "Router Renumbering for IPv6", RFC 2894,
             August 2000.



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   [RFC2874] Crawford, M., and C. Huitema, "DNS Extensions to Support
             IPv6 Address Aggregation and Renumbering", RFC 2874, July
             2000.

   [RFC3007] B. Wellington, "Secure Domain Name System (DNS) Dynamic
             Update", RFC 3007, November 2000.

   [RFC3315] R. Droms, Bound, J., Volz, B., Lemon, T., Perkins, C., and
             M. Carney, "Dynamic Host Configuration Protocol for IPv6
             (DHCPv6)", RFC 3315, July 2003.

   [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
             Host Configuration Protocol (DHCP) version 6", RFC 3633,
             December 2003.

   [RFC3956] P. Savola, and B. Haberman. "Embedding the Rendezvous Point
             (RP) Address in an IPv6 Multicast Address.", RFC 3956,
             November 2004.

   [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander
             "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
             "Neighbor Discovery for IP version 6 (IPv6)", RFC
             4861,September 2007.

   [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
             Address Autoconfiguration", RFC 4862, September 2007.

12.2. Informative References

   [RFC2072] H. Berkowitz, "Router Renumbering Guide", RFC2072, January
             1997.

   [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
             Renumbering an IPv6 Network without a Flag Day", RFC 4192,
             September 2005.

   [RFC4714] Enns, R., "NETCONF Configuration Protocol", RFC 4714,
             December 2006.

   [RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering
             Still Needs Work", RFC 5887, May 2010.

   [I-D.ietf-dhc-secure-dhcpv6]
             Jiang, S., and Shen S., "Secure DHCPv6 Using CGAs", working
             in progress.


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   [I-D.chown-v6ops-renumber-thinkabout]
             Chown, T., "Things to think about when Renumbering an IPv6
             network", Work in Progress, September 2006.

   [I-D.jiang-6renum-enterprise]
             Jiang, S., and B. Liu, "IPv6 Enterprise Network Renumbering
             Scenarios and Guidelines ", Working in
             Progress, July 2011.

   [I-D.carpenter-6renum-static-problem]
             Carpenter, B., and S. Jiang, "Problem Statement for
             Renumbering IPv6 Hosts with Static Addresses", Working in
             Progress, October 2011.

   [LEROY]  Leroy, D. and O. Bonaventure, "Preparing network
             configurations for IPv6 renumbering", International of
             Network Management, 2009, <http://
             inl.info.ucl.ac.be/system/files/dleroy-nem-2009.pdf>

13. Acknowledgments

   This work adopts significant amounts of content from [RFC5887] and
   [I-D.chown-v6ops-renumber-thinkabout], so thank for Brian Carpenter,
   Randall Atkinson, Hannu Flinck, Tim Chown, Mark Thompson, Alan Ford,
   and Stig Venaas. Some useful materials were provided by Oliver
   Bonaventure and his student Damien Leroy, thanks for them, too.

   Useful comments and contributions were made by Wesley George, and
   others.

   This document was prepared using 2-Word-v2.0.template.dot.

















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Internet-Draft   IPv6 Site Renumbering Gap Analysis      December 2011


Authors' Addresses

   Bing Liu
   Q14-4-A Building
   Huawei Technologies Co., Ltd
   Zhong-Guan-Cun Environment Protection Park, No.156 Beiqing Rd.
   Hai-Dian District, Beijing
   P.R. China
   Email: leo.liubing@huawei.com


   Sheng Jiang
   Q14-4-A Building
   Huawei Technologies Co., Ltd
   Zhong-Guan-Cun Environment Protection Park, No.156 Beiqing Rd.
   Hai-Dian District, Beijing
   P.R. China
   Email: shengjiang@huawei.com


   Brian Carpenter
   Department of Computer Science
   University of Auckland
   PB 92019
   Auckland, 1142
   New Zealand
   EMail: brian.e.carpenter@gmail.com


















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